1. Field of the Invention
The present invention generally relates to a method for forming photoresist patterns, and more particularly, to a method for forming photoresist patterns adopting immersion photolithography.
2. Description of the Prior Art
Photolithography is one of most essential or critical processes in the semiconductor manufacture. The photolithography not only positively influences the process result as well the performance of the ion implantation or etching process but also positively influences the performance and reliability of the final semiconductor devices. Furthermore, the photolithography renders impacts to device integration as well to the progression of semiconductor fabrication. For example, conventional semiconductor fabrication processes typically employ g-line photography having wavelengths of 465 nanometer (nm). And the conventional semiconductor fabrication processes further develop i-line photolithography having wavelengths of 365 nm, 248 nm and 193 nm for fulfilling the requirement of high resolution to the trend of device miniaturization.
However, it is found that as the wavelength becomes shorter, the energy of the provided UV becomes greater and therefore the reflected light from the material under the photoresist is increased. Consequently the reflected UV renders serious interference to the incident UV light and critical dimension (CD) shift is resulted, which forms inaccurate patterns after the photolithography. And the following process such as ion implantation and etching process are adversely impacted.
As a countermeasure against to the abovementioned problems, there has been proposed a multilayered bottom anti-reflective coating (hereinafter abbreviated as BARC) for reducing reflectivity before forming the photoresist. The BARC conventionally includes inorganic materials and is formed as a multilayered structure to provide sufficient ability to reduce UB reflectivity and to avoid thickness control difficulty.
It is well known to those skilled in the art that the BARC is eventually removed as well as the photoresist and followed by other required processes. Therefore it is still in need to provide a method for forming photoresist patterns that is able to reduce the process cost on the temporary BARC without influencing the accuracy of the transferred photoresist patterns.